Is the Modified Early Warning Score (MEWS) superior to clinician judgement in detecting critical illness in the pre-hospital environment?

doi:10.1016/j.resuscitation.2012.01.004

Resuscitation

Volume 83, Issue 5, May 2012, Pages 557-562

https://doi.org/10.1016/j.resuscitation.2012.01.004 Get rights and content

Abstract

Aim

Physiological track and trigger scores have an established role in enhancing the detection of critical illness in hospitalized patients. Their potential to identify individuals at risk of clinical deterioration in the pre-hospital environment is unknown. This study compared the predictive accuracy of the Modified Early Warning Score (MEWS) with current clinical practice.

Methods

A retrospective observational cohort study of consecutive adult (≥16 yrs) emergency department attendances to a single centre over a two-month period. The outcome of interest was the occurrence or not of an adverse event within 24 h of admission. Hospital pre-alerting was used as a measure of current critical illness detection and its accuracy compared with MEWS scores calculated from pre-hospital observations.

Results

3504 patients were included in the study. 76 (2.5%) suffered an adverse event within 24 h of admission. Paramedics pre-alerted the hospital in 224 cases (7.3%). Clinical judgement demonstrated a sensitivity of 61.8% (95% CI 51.0–72.8%) with a specificity of 94.1% (95% CI 93.2–94.9%). MEWS was a good predictor of adverse outcomes and hence critical illness detection (AUC 0.799, 95% CI 0.738–0.856). Combination systems of MEWS and clinical judgement may be effective MEWS ≥4 + clinical judgement: sensitivity 72.4% (95% CI 62.5–82.7%), specificity 84.8% (95% CI 83.52–86.1%).

Conclusions

Clinical judgement alone has a low sensitivity for critical illness in the pre-hospital environment. The addition of MEWS improves detection at the expense of reduced specificity. The optimal scoring system to be employed in this setting is yet to be elucidated.

Introduction

Ambulance crews and pre-hospital clinicians often represent the first point of contact with medical services. In the pre-hospital environment key decisions regarding commencement of therapy and both priority and destination of patient transfer are often made in the absence of full clinical information, by staff with varying degrees of training and expertise. Such judgements are largely based on subjective processes, clinical experience and are rarely evidence based.1, 2, 3

Several studies have raised concern that the severity of a patient's illness, especially those presenting with medical (non-trauma) pathology, is currently being overlooked by pre-hospital staff.1, 4, 5 Subsequent transfer to hospitals with limited critical care resources and experience, or delayed identification and referral to critical care following arrival may ensue, with associated adverse outcomes.6, 7, 8 This is in sharp contrast to pathology-specific protocols, such as stroke or myocardial infarction, where diagnoses are often accurately made, appropriate management administered, and patients conveyed to suitable receiving centres with attendant improvements in morbidity and mortality.9, 10

‘Early warning score’ or ‘track and trigger systems’ aim to aid the timely recognition of patients with potential or established critical illness. They allow the risk of deterioration in heterogeneous groups of patients to be quantified on a numerical scale and, via pre-defined escalation protocols, facilitate objective decision-making to ensure a suitable clinical response.11, 12 Appropriately derived and validated scores may help to optimise individual patient management through improved risk stratification and prognostication from point of admission: guiding resource allocation and place-of-care whilst simultaneously providing a benchmarking tool for research, audit and standardisation of care across healthcare organisations.⁵

The role of physiological track and trigger systems (PTTS) and their implementation in clinical practice has been expanding rapidly under the influence of various political initiatives, healthcare organisations and think-tanks.13, 14, 15, 16 Their use on both medical and surgical wards is well established17, 18, 19 if not clearly validated.11, 12, 20 Interest in their role at point of admission is growing, especially in medical patients and those with suspected sepsis, but requires further work to achieve true clinical utility.5, 21, 22, 23, 24, 25 Despite the obvious potential, their role in facilitating more objective evidence-based decision making and triage in the pre-hospital environment has only recently been considered.26, 27

UK ambulance crews directly or in-directly (via a dispatch centre) pre-alert receiving centres when transporting individuals they determine to be critically unwell or with time-critical pathology.28, 29 No standardised protocol describing indications for pre-alert to hospitals currently exists and decisions are based on subjective criteria.¹ Ambulance crews’ pre-alerting of hospitals thus represents a measure of the current accuracy of clinical detection of critical illness in the pre-hospital environment and offers a paradigm against which alternative methods may be tested.

This study seeks to assess whether one example of an aggregate-weighted PTTS, the Modified Early Warning Score (MEWS),¹⁸ is superior to clinician assessment in detecting critical illness in the pre-hospital environment.

Section snippets

Design and subjects

A retrospective observational cohort study of consecutive adult attendances (≥16 yrs) of all aetiologies to Birmingham Heartlands Hospital between April and June 2010. Heartlands Hospital is an 800 bed inner city NHS hospital in the UK. The Emergency Department (ED) treats approximately 115,000 patients a year. Patients who had clinical observations undertaken and recorded by ambulance staff prior to arrival at hospital were eligible for inclusion. Patients in cardiac arrest (receiving CPR)

Results

5170 patients were brought to hospital during the study period. 3504 patients had clinical observations undertaken, recorded by ambulance staff and scanned by ED staff making them eligible for study inclusion. Twenty-six (0.7%) patients were excluded due to missing outcome data. Of the 3478 cases remaining, a number of patients had more than one record in the data file due to multiple admissions, as identified by the patient identification numbers. For each patient, only the first record was

Discussion

This study is the first to test an established PTTS against clinical judgement, and attempt to establish its role as a decision-making tool in the detection of critical illness in the pre-hospital environment.

In common with previous studies we have highlighted a failure to predict adverse outcomes by pre-hospital practitioner clinical judgement alone. 76 patients (2.5%) in this study suffered an adverse event within 24 h of hospital admission and paramedics alerted the hospital to a patient's

Conclusions

Current rates of critical illness detection and outcome prediction in the pre-hospital environment are low. The addition of MEWS to clinical assessment improves sensitivity, particularly to medical pathology, at the expense of increased clinical resource expenditure. The secondary benefits afforded by PTTS are considerable and come at little expense. The optimal scoring system to be employed in this setting is yet to be elucidated.

Conflict of interest

No conflicting interests to declare. Full control over the primary data is retained by the authors.

Acknowledgements

We would like to especially thank Dr. Peng Dong for her help with data collection and the team at the Academic Department of Anaesthesia, Critical Care, Pain and Resuscitation at Heartlands Hospital for their support. GDP is funded by a Department of Health, National Institute for Health Research Clinician Scientist Award. No funding was received in support of this manuscript

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To determine the rate and predictors of death in older individuals with suspected infection at any time during hospital stay in a geriatric acute ward and the prognostic ability of different tools [quick Sequential (Sepsis-related) Organ Failure Assessment (qSOFA), Modified and National Early Warning Scores (MEWS) and (NEWS)] in such population.
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Among 305 older inpatients (median age 86.0 years, 49.2% female), 21% died during hospital stay. Sepsis was diagnosed in 31.8% of the overall sample and in 64.1% of deceased patients. Deceased patients showed a significantly higher prevalence of prior institutionalization, functional dependence, cognitive impairment, and multimorbidity. The prognostic accuracy of the qSOFA score at infection onset was only fair (area under the receiver operating characteristic curve 0.72; 95% CI, 0.65–0.79, P < .001) and comparable with that of MEWS and NEWS. After multivariable analysis, in-hospital death was positively associated with male sex [odds ratio (OR), 2.11; 95% CI, 1.01–4.44; P = .048] and abnormal white blood cells count (OR, 4.93; 95% CI, 2.36–10.29; P < .001), platelet count (OR, 2.61; 95% CI, 1.10–6.16; P = .029) and serum creatinine (OR, 2.70; 95% CI, 1.30–5.61; P = .008), along with any of the score considered, and negatively associated with autonomy in instrumental activities (OR, 0.78; 95% CI, 0.68–0.90; P < .001).
Prognosis in older inpatients with infection or sepsis appears to be determined both by the geriatric characteristics and by the severity of the acute event, expressed by recommended tools and blood test results.
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Citation Excerpt :
The predicted outcome in our study was associated with short-term mortality and our prediction model demonstrated excellent discriminatory performance. The prediction model in our study had relatively higher sensitivity and specificity when compared with most of the EWSs developed for prehospital settings that we found in the literature.9–14 However, in both the derivation and validation cohorts, the PPVs were low because of our low event rate.
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^☆: A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2012.01.004.

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Clinical paperIs the Modified Early Warning Score (MEWS) superior to clinician judgement in detecting critical illness in the pre-hospital environment?☆

Abstract

Aim

Methods

Results

Conclusions

Introduction

Section snippets

Design and subjects

Results

Discussion

Conclusions

Conflict of interest

Acknowledgements

Injury

Resuscitation

Resuscitation

Resuscitation

Blue calls – time for a change?

Emerg Med J

Paramedic determinations of medical necessity: a meta-analysis

Prehosp Emerg Care

Ambulance alerting to hospital: the need for clearer guidance

Emerg Med J

Predictive scoring in non-trauma emergency patients: a scoping review

Emerg Med J

Hospital volume and the outcomes of mechanical ventilation

N Engl J Med

Confidential inquiry into quality of care before admission to intensive care

BMJ

Outcome of emergency department patients with delayed admission to an intensive care unit

Emerg Med

Rural PAST Protocol Steering Group.The rural Prehospital Acute Stroke Triage (PAST) trial protocol: a controlled trial for rapid facilitated transport of rural acute stroke patients to a regional stroke centre

Int J Stroke

Prehospital triage in the ambulance reduces infarct size and improves clinical outcome

Am Heart J

Detecting critical illness outside the ICU: the role of track and trigger systems

Curr Opin Crit Care

Circulation

The value of Modified Early Warning Score (MEWS) in surgical in-patients: a prospective observational study

Ann R Coll Surg Engl

Clinical paper
Is the Modified Early Warning Score (MEWS) superior to clinician judgement in detecting critical illness in the pre-hospital environment?☆